In a single stage machine a tire is constructed in a generally continuous process being initially built flat or cylindrical and then shaped to its toroidal shape for final application of the belt and tread assembly either separately constructed or constructed directly on the tire after thus shaped. In a first stage machine the tire is constructed in a cylindrical or flat band form and then removed to a second stage machine or shaper wherein it is converted to toroidal shape for final application of components such as the belt and tread assembly.
Whether the machine be single, first or second stage, the beads of the tire must be properly supported and locked for the application or wrapping of the components thereabout. In a single or second stage machine, the bead locks move uniformly toward each other as the tire is expanded and converted from its generally cylindrical to a toroidal or tire shape. Regardless of the type of machine utilized, the beads must be precisely held and positioned both with respect to the axial centerline of the machine as well as the transverse centerline. The beads must be equidistant from the transverse centerline which is through the crown of the tire. In addition, the bead locks in the shaping operation without a shaping sleeve desirably provide an air seal so that air under pressure within the tire will shape it to its desired toroidal shape.
Radially expandable bead locks have been employed in tire construction and reference may be had to the following U.S. patents as examples of such bead lock constructions employed: U.S. Pat. Nos. Giletta et al 3,134,079; Olbert et al 3,853,653; Caretta et al 3,433,695; Henley 3,402,090; Held et al 3,862,871; Vanzo et al 3,035,629; and Cantarutti 3,721,600.
It is also known to provide tire building machines which include a radially expansible center deck such as seen in Burton U.S. Pat. No. 3,160,545, Appleby et al U.S. Pat. No. 3,784,437, and Jones et al U.S. Pat No. 3,740,293. Also, some center decks collapse axially as the tire is expanded as seen, for example, in Galleithner et al U.S. Pat. No. 3,864,189 and the above noted Appleby patent. Some are axially adjustable in length as seen in Gazuit U.S. Pat. No. 3,647,598.
Where an elastomeric bead lock is employed, because of the inherent nature of any rubber band, it is difficult properly to seat and control the expansion and contraction of the bead lock to obtain precise centering of the beads both radially and axially. Any rubber band when elongated, narrows in cross section and accordingly the dimensions in the stressed and unstressed conditions are not the same. Also, when the bead lock includes an integrally formed shaping bladder, it is difficult to supply such bladder with inflation air pressure without unduly confining it thus precluding it from doing its desired function. The bladder is usually inherently restricted by an inlet or stem offset from the bead lock as seen in French Pat. No. 2,227,121 dated Apr. 22, 1974, or in the above noted Cantarutti U.S. Pat. No. 3,721,600.
Further, in a single stage machine, particularly when constructing larger and more complex tires, it is desirable to apply tire components such as chafers, body plies, or belt cushions which should desirably be stitched. Accordingly, between such bead locks there should be a center deck which is substantially rigid throughout its length to permit such stitching and yet which will axially contract as the tire is brought to its toroidal shape.